French officials have confirmed that they are investigating a terrorist attack and there are unconfirmed reports that there are gunmen on the loose in the city.

French TV channel iTele tonight reported that a gunman “holed up in a nice restaurant downtown” had been “neutralized” by police.

The channel said it is not believed the man had taken any hostages during the incident.

On the promenade it is thought that police officers desperately fired on the truck as it was “deliberately driven” for more than 100 metres at people leaving a major bank holiday fireworks celebration.

Witnesses said the truck picked up speed and “rammed” the crowd where it was thickest at more than 30mph, and images emerged of the cab riddled with bullets. One said he saw the driver emerge with a gun after the truck came to a halt and begin shooting at the fleeing crowd.

Police have identified the driver, who was killed during the incident, and it is believed to have been a man who was known to security services. Separate reports emerged tonight that police fear four different trucks are involved, raising fears of a massive organised terror attack.

Crowds had packed out the city’s main promenade to watch a fireworks display marking Bastille Day, a major public holiday in France, and were beginning to head home when the lorry hit.

One witness reported horrific scenes with “dead bodies everywhere” and distressing video footage emerged of people fleeing the Promenade des Anglais, in the southern French city, in terror.